For several hundred years, stair systems employing nose molding have been constructed in a similar manner by the same basic method.
Referring to FIGS. 1 and 2, a stair system is supported by stringers 12, having tread sides 14 cut out, on which are secured tread subflooring 104 and tread 108 and riser sides 15 cut out, on which are secured riser subflooring 106 and risers 112. The riser subflooring 106 is secured to the riser side 15 of the stringers and the tread subflooring 104 is secured to the tread side 14 of the stringer. Subflooring is normally secured by nailing, screwing, and/or with the use of adhesives. Stairs are normally built from the top down. The hardwood floor at the top of the stairs is built to within about one to two inches of the edge of the stair top. The end of the hardwood flooring which is on top of the subflooring on top of the stairs is mated with and covered with the conventional stair nose 114 which has a bottom lip 116 and a top lip 118. The top lip 118 covers and engages the end of the hardwood flooring. The stair nose is secured to the subflooring either with glue and/or nails 22. Glue is used because it eliminates face nailing, i.e., the step of countersinking the nail and filling in the countersink area. However, the gluing must be done well because the stair nose, which is relatively large, takes great stresses as a person steps on the stair nose when descending or ascending the stairs. Because of the tendency of natural wood to expand and contract with changes in humidity and temperature, the large wood stair nose and natural wood tread and riser are constantly working and eventually can loosen the adhesive bond between the stair nose and subflooring. The stair nose is secured to the subflooring at the top of the stairs so that there is sufficient room between the edge of the subflooring 104 and the first subflooring riser 106 and the lip 116 to receive the top edge finished riser 112. A space of 1/4 inch to 1/8 inch is left between the edge of the flooring at the top of the stairs and the back end 119 of the stair molding to provide expansion space for the floor. A space of 3/16 to 1/16 inch is left between the top edge 113 of the riser and the bottom side 115 of the stair nose molding to provide expansion space for the riser.
The first step below the top of the stairs is constructed by sizing and cutting the finished riser 112, and inserting the top edge of the riser into the space between the front edge of the subflooring at the top of the stair and the lip 116. The riser must be cut within a 1/8 inch to provide expansion space 113. The bottom of the riser rests on foam pad 110. The riser is preferably nailed into the subflooring 106 with a nail 22, as shown in FIG. 1, or glued to the subflooring. The nail 22 nail can be hidden by the finished tread 108 in which case it does not have to be countersunk. The finished tread 108 for the first step is cut to size and laid down over the tread subflooring 104 with a foam padding 110 disposed between the finished tread subflooring. The foam pad is optional. The finished tread must be cut neatly and square at its back edge. The rear of the tread 108 is secured to the subflooring by nail 22. If desired, the nail hole can be covered with molding (not shown). However, the molding must be face nailed requiring counter sinking the nail and filling the counter sunk hole. The front of the tread 108 is held down by the underside of lip 118 of the stair nose. A small amount of space from 1/8 to 1/4 inch is left between the back side 119 of the stair nose 114 and the front side of the tread 108 to allow for expansion of the tread 108. Most treads, as well as stair nose, molding and risers, are made of wood, especially hardwood. This wood is normally kiln-dried. Depending upon the humidity of the environment, the wood can absorb or lose moisture, thus expanding or contracting the wood. Stair nose molding 114 can be secured in the subflooring by nail 22 and/or adhesive applied to the underside 115 of the stair nose, nailing is preferred because of the stresses placed on the stair nose when a person steps on it. The point A is a fulcrum about which the stair nose attempts to pivot when a person steps on the front half of the stair nose. This places great force on the back half of the stair nose, tending to force it to pivot upward as the front half tends to be forced downward.
For the next stair, the operation is repeated. The finished riser 112A is cut to size, the top of the riser is inserted into the groove between lip 116 and the front edge of the subflooring 104. The bottom of the riser 112A rests on the subflooring 104 with foam pad 110 disposed between the bottom edge and the subflooring. The riser is secured to the subflooring. The finished tread 108 is cut and sized and positioned onto the subflooring 104 of the second step with the foam pad 110 disposed between. The back edge of the finished tread must be cut precisely to obtain a neat joint with the riser. The stair nose molding is then secured to the front of the stairs with the lip 116 engaging the top of the finished tread 108. Sufficient space is left between the lip 116 of the stair nose molding and the stair subflooring to allow for the next riser to be inserted in the space between the lip and the subflooring as described above.
Natural wood staircases are very attractive but environmentally destructive because of the amount of clear grain wood they require. Even veneer plywood treads and risers require a clear grain veneer wear surface. The large conventional hardwood stair noses require substantial amounts of kiln-dried clear grain hardwood.
FIG. 2 shows an alternative embodiment of the prior art stair system. The stair system is very similar to the stair system shown in FIG. 1, except that the finished tread is applied directly to the subflooring 104, i.e., it has no foam pad disposed between the tread and the subflooring. The stair nose 122 does not have an upper lip 118. The back of the stair nose has a tongue 124 for a tongue and groove system. The edge of the tread, and the hardwood flooring at the top step also, have a groove 126 adapted to receive the tongue 124. This type of stair nose is normally not used with free-floating treads as in FIG. 1. Tread 108 is secured to the subflooring with nails and/or adhesive. Stair nose 122 can be secured to the subflooring either with adhesive applied to the lower surface 115 or with nails. Nailing is preferred because of the great stresses placed on the relatively long stair nose as for the same reasons described above with respect to the stair nose of FIG. 1. The union between the stair nose and the front edge of the tread 108 requires careful shaping and sawing so that the back side of the stair nose mates evenly with the front side of the tread 108. If back stair molding 120 is not used, the back edge of the tread requires careful shaping and cutting so that the joint with the riser is neat and decoratively pleasing. In all other respects, this stair system is identical to the stair system shown in FIG. 1.
Although the above stair systems have been used for many, many years, they are not perfect. The system of FIG. 1 permits the tread and riser to be free-floating, thus allowing them to contract and expand with changing temperature and humidity conditions in the environment. However, the lip 118 is not an attractive feature and it has some safety problems since it requires a person descending the floor to raise his or her heel to clear the lip when descending the stairs. A heel can tangled up with lip 118 and cause a person to fall. In addition, the constant hitting of the lip 118 with heels of shoes causes uneven wear to the lip.
The stair system of FIG. 2 is more attractive and does not have the disadvantages of the lip design of the stair molding 114. However, this system does not permit the tread to be free-floating. The tread must be secured to the subflooring 104, either with glue and/or with nails. The securing of the tread to the subflooring does not stop the tread from expanding and contracting with environmental changes. This loosens the tread from the subflooring with usage and time.
The finished carpentry industry for years has been looking for a system that would permit the use of free-floating tread that would compensate for contraction and expansion of the tread with changing temperature and humidity conditions, and yet allow the top of the stair nose and the tread to be coplanar, i.e., even, to give a more attractive finish, to give better wear qualities, and to avoid any potential hazard with the hang-up of the lip, such as shown in FIG. 1.
The finished carpentry industry has been looking for a composite tread and rider stair that does not expand and contract like wood plank stair systems and would minimize the use of clear grain hardwoods.
It is one object of the present invention to provide a stair system with a free-floating tread that does not require glue or adhesive between the tread and subflooring.
It is the object of the present invention to provide a stair system wherein the stair nose, tread and riser may be secured to the stair subflooring with adhesives alone.
It is another object of the present invention to provide a decorative wooden staircase with the minimum use of expensive axle wood, especially large decoratively pleasing wooden planks for the tread, riser and/or stair nose.
It is still a further object of the present invention to provide a stair system that has a small stair nose in order to minimize the forces exerted on the stair nose when a person steps on the stair nose when ascending or descending the stairs.
It is still a further object of the present invention to provide a stair nose system where the bulk of the wear on the stair will be taken by the tread rather than by the stair nose.
It is an object of the present invention to provide a stair system which utilizes the stringers and subflooring of the existing stair systems.
It is another object of the present invention to provide an improved stair system which permits the stairs to be built without precision cutting.
It is a further object of the present invention to provide a stair system where the riser is free-floating and not secured to the stair subfloor.
It is another object of the present invention to provide an improved stair system which permits the center portion of the tread to be free-floating.
It is a further object of the present invention to provide an improved stair nose which permits the stair system to be built with a tread having its center portion free-floating and having the top of the stair nose and the tread in the same plane.
It is still another object of the present invention to provide a simplified system of securing the back of the tread to the subflooring and to hide it with an attractive molding.
It is still another object of the present invention to provide a method of installing a finished tread and riser with rough cutting and a minimum of accurate cutting so that the stair system can be quickly installed.
An even further object of the present invention is to provide a stair system wherein the back edge of the tread does not have to be neatly or accurately cut to size to yield an attractive and secure stair system.